Ordering 'Species' Section of .msx File

[henryricca]

We have noticed behavior with MSX where the order of the species in the [SPECIES] section of the .msx input file appears to impact the results. The only difference between chloramine.msx and chloramine_ordered.msx (both attached) is the ordering of the species in the [SPECIES] section, but they produce different results. In the "_ordered" file, species are ordered in the same order as the reactions specified in the [PIPES] section. However, this ordering produces negative concentrations for some species. The following 5 files are in the attached .zip folder, which highlight the issue.

chloramine.inp - EPANET input file for the simple example network provided with the manual

chloramine.msx - MSX input file with an ordering that seems to produce stable results for monochloramine decomposition

chloramine_ordered.msx - MSX input file with an ordering that seems to produce negative concentrations for some species for monochloramine decomposition

chloramine.rpt - report file generated from running 'chloramine.inp' with 'chloramine.msx'

chloramine_ordered.rpt - report file generated from running 'chloramine.inp' with 'chloramine_ordered.msx'

Species_Order_Issue.zip